#529 - Toxics Affect Behavior, 15-Jan-1997

The toxic metal, lead, is associated with aggressive behavior,
delinquency, and attention disorders in boys between the ages of 7 and
11, according to a study by Herbert Needleman published in 1996 in the
JOURNAL OF THE AMERICAN MEDICAL ASSOCIATION (JAMA).[1] Aggressive
behavior, delinquency and attention disorders in youth are, themselves,
predictors of criminal behavior later in life.[2] This is not the first
study linking lead exposure to behavioral disorders, but it is one of
the most carefully done.

Needleman's study examined 301 boys in public schools in Pittsburgh,
Pennsylvania, measuring the lead in their bones and relating it to
behaviors reported by the boys' teachers and parents, and by the boys
themselves. Boys with more lead in their bones consistently had more
reports of aggressive and delinquent behavior, and problems paying
attention. The boys' behavior was measured at age 7 and again at age
11, and the behavior of boys with more lead in their bones got worse as
they grew older; on the other hand, behavior did not change among boys
with less lead in their bones.

Aggressive behavior, delinquency, and attention disorders in boys and
young men are also associated with poverty, minority status, and
disorganized homes, so lead is not the only factor at work in many
cases. However, the 1996 Needleman study examined 9 variables in
addition to lead (such as parent's socioeconomic status, mother's age,
presence or absence of a father in the home, and so forth), to see if
they might explain the boys' behavior. The relationship between lead
and behavior disorders held up.

"These data argue that environmental lead exposure, a preventable
occurrence, should be included when considering the many factors
contributing to delinquent behavior," the authors of the study said.

What is remarkable is the degree to which environmental lead exposure
has been ignored in the past by people concerned about the growing
problem of aggressive, anti-social behavior in boys and young men in
the U.S. An estimated 20% of American children now exhibit mental or
behavioral problems.[3] As early as 1943, Randolph Byers and Elizabeth
Lord[4] examined 20 children who had recovered from "mild lead
poisoning in infancy." They reported that none of the children had
exhibited overt signs of lead poisoning, yet the growth and development
of their nervous systems had been "seriously impaired." Among the 20
children examined, only one had progressed satisfactorily in school.
Furthermore, many of the children were emotionally impaired as well.
Byers and Lord characterized the behavior of many of the children as
"unreliable impulsive behavior, cruel impulsive behavior, short
attention span, and the like." Three of the 20 children were expelled
from school, one for setting fires, another for repeatedly getting up
and dancing on the desks, and a third for sticking a fork into another
child's face. In 1986, Byers recalled that others in the group he had
studied in 1943 had attacked teachers with knives and scissors.[5]
Byers's 1943 report should have set off alarm bells, but it didn't.

After the 1943 report, for the most part lead researchers ignored the
newly-revealed connection between lead, aggressive behavior and
impaired attention. Instead they went on to demonstrate conclusively
that intellectual power (as measured by IQ) was consistently reduced by
exposure to low levels of lead. For every 10 microgram rise (in each
deciliter of blood), there is a 6 point loss of IQ.[6] [A deciliter is
a 10th of a liter, and a liter is about a quart.] Reduced IQ power can
be measured when lead is as low as 7 micrograms per deciliter of blood
(7 ug/dl).[7] In fact, there is no apparent threshold for this effect:
any amount of lead seems to diminish mental power in children.[8]
Furthermore, brain damage from lead exposure persists for many years;
the IQ reduction caused by lead in childhood is essentially permanent.
[9]

Nevertheless, some work on lead and behavioral disorders did appear:
[10]

** In Virginia in 1975, researchers compared 67 lead-exposed 7-year-
olds to 70 non-exposed children to see if lead exposure was related to
increased behavior problems in school.[11] Nineteen of the lead-exposed
children were described as "hyperactive, impulsive, and explosive, and
as having frequent temper tantrums." Only five among the non-exposed
group were described this way.

The group was re-evaluated a year later, emphasizing behavior in the
home. The examination of 8-year-olds revealed 14 lead-exposed children
with "severe abnormalities," defined as lying, stealing, running away,
and setting fires, vs. six with such abnormalities among the non-
exposed group.

** In rural Tennessee in 1982, researchers asked teachers to identify
"problem children" among their students, using the Walker Problem
Behavior Identification Checklist, a screening device designed for
elementary school teachers to help them identify troubled kids. Average
lead levels in the hair of 26 "problem children" was nearly twice as
high (11.6 ppm vs. 6.5 ppm) as in a control group of 29 students
identified as not having problems.[12]

** In Scotland in 1989, researchers showed that lead was related to
attention disorders and aggressive behavior (as reported by parents and
teachers) among a group of 501 students between the ages of six and
nine. These children had average (mean) blood lead levels of 10.4
ug/dl.[13]

** In Baltimore in 1992, blood lead levels among 201 African-American
children aged two to five were compared to the children's behavior as
reported by their mothers on a well-known standardized questionnaire
(the Child Behavior Checklist, or CBCL).[14] Of these, 123 were in the
"high exposure" group (blood lead levels of 15 ug/dl, or more) and 78
were in a "low exposure" group. The high-lead group consistently had
more maternal-reported troublesome behaviors. For example, 8.1% of the
high-lead group were "aggressive" vs. 1.4% in the low-lead group.
Mothers reported 4.1% of the high-lead children had "destructive"
behavior vs. no such behavior in the low-lead group.

** In New Zealand in 1993, researchers examined lead in the teeth of
1265 children aged 6-8, compared to behavior of those children as
measured seven years later.[15] They found a small but consistent
relationship between increasing lead and increasing social adjustment
problems in youngsters.

** In Boston in 1994, a study of 1782 children related the amount of
lead in their teeth to behavior in school (using the CBCL).[3] Problem
behaviors increased systematically as lead levels in the children's
teeth increased.

In recent years, lead in the blood of Americans has diminished
substantially, because the government outlawed lead in gasoline and
lead in tinned cans used for food.[16] The biggest reduction has
occurred among white children, but all populations have benefitted to
some extent. Nevertheless, in 1994, an estimated 1.7 million American
children between the ages of one and five (mostly African Americans
living in large cities) had average blood lead levels of 10 ug/dl or
more, and a million children had blood lead levels of 15 ug/dl or more.
Among African American children in large cities, 36.7% have blood lead
levels above 10 ug/dl, and 17.0% of Mexican-American children in large
cities have similar levels of toxic lead in their blood.[17]

In the mid-1970s, 40% of American children under age 5 had average
(mean) lead levels of 20 ug/dl or more.[18] Among African-American
children in the mid-1970s, more than half had blood-lead levels greater
than 15 ug/dl.[16] This is the generation that is presently in its mid-
20s. How is this generation doing?

In 1993, 1.53 million Americans were in jail or prison --triple the
number that had been incarcerated in 1980.[19] In 1980, one in every
453 Americans was in state or federal prison; by 1993, the number had
risen to one in every 189.[20] In 1993, the incarceration rate among
blacks was seven times as high as among whites. Between 1990 and 1993,
the number of drug offenders increased dramatically by 55,500, but the
number of violent offenders grew even more rapidly (by 82,100). In
1994, the prison/jail population increased at the rate of 1600 each
week and almost 1200 (75%) of these new inmates were black or hispanic.

It seems possible that the observed connection between brain-damaging
lead and destructive behavior explains a portion of these increases.
[21]

Prevention is the key. The main source of the toxic lead in children
today is dust and soil,[22] but the source of the lead in the dust and
soil is lead-based paint coming out of older buildings.[23] The federal
Centers for Disease Control (CDC) in Atlanta has calculated the cost of
removing all lead-based paint from old buildings, along with the
benefits that society would realize from such a removal (reduced costs
for medical care and for special education, plus increased salaries
that go with higher IQs). According to CDC, American taxpayers would
realize a net profit of $28 billion by removing all lead-based paint.
[24]

[9] Herbert L. Needleman and others, "The Long-term Effects of Exposure
to Low Doses of Lead in Childhood," NEW ENGLAND JOURNAL OF MEDICINE
Vol. 322, No. 2 (1990), pgs. 83-88.

[10] The few studies examining lead and behavior in the period 1944-
1980 are reviewed in Herbert L. Needleman and Philip J. Landrigan, "The
Health Effects of Low Level Exposure to Lead," ANNUAL REVIEW OF PUBLIC
HEALTH Vol. 2 (1981), pgs. 277-298.

[23] Brian L. Gulson and others, "Paint as a source of recontamination
of houses in urban environments and its role in maintaining elevated
blood leads in children," SCIENCE OF THE TOTAL ENVIRONMENT Vol. 164
(1995), pgs. 221-235.